Fixation or fusion of vertebral columns with bone or material, rods or plates is a common, long practiced surgical method for treating a variety of conditions. Many of the existing procedures involve the use of components that protrude outwardly, which may contact and damage a body part, such as the aorta, the vena cava, the sympathetic nerves, the lungs, the esophagus, the intestine and the ureter. Also, many constructions involve components that may loosen and cause undesirable problems, often-necessitating further surgical intervention. Additionally, limiting the success of these procedures are the biomechanical features of the spine itself, whose structure must simultaneously provide support to regions of the body, protect the vertebral nervous system and permit motion in multiple planes.
As indicated above, spinal surgery for spine fusion generally involves using implants and instrumentation to provide support to the affected area of the spine while allowing the bones thereof to fuse. The technology initially evolved using bone chips around and on top of an area of the spine that had been roughened to simulate a fracture in its consistency. The area, having encountered the bone chips, would then proceed to heal like a fracture, incorporating the bone chips. However, surgical procedures dealing with the spine present notable challenges. For example, bioengineers have been required to identify the various elements of the complex motions that the spine performs, and the components of the complex forces it bears. This complexity has made it difficult to achieve adequate stability and effective healing in surgical procedures directed to the spine.
One surgical technique provided by Cloward, involves cutting a dowel type hole with a saw across or through the moveable intervertebral disc and replacing it with a bone graft that was harvested from the hip bone. This procedure results in a fusion of the adjacent vertebral bodies and limits motion and mobility. However, as a result of the complex motions of the spine, it is often difficult to secure the dowel from displacing. Further, it has become apparent over time, however, that this particular technique does not always yield a secure fusion.
Other techniques have been developed that involve the placement of various hardware elements, including rods and hooks, rods and screws and plates and screws. The dowel technique also has advanced over the past five years or so, with dowels being fabricated from cadaver bone or metals such as titanium or stainless steel. These techniques, whether using hardware, dowels or some combination thereof, have a common goal to enhance stability by diminishing movement, thereby resulting in or enhancing the potential of a fusion of adjacent vertebral bones. For example, in one of these other techniques, the disc is removed and adjacent vertebrae are positioned in a stable position by placing a plate against and traversing them, which plate is secured or anchored to each by means of screws.
In another procedure, cages in the form of two parallel circular or rectangular devices are made out of a material such as titanium or stainless steel and these devices are fenestrated. Bone is packed in the center of the devices that will heal to adjacent bone through each fenestration. In this procedure, the disc space is distracted so all ligamentous structures are taut and the bones are held in their normal maximal position of distraction. Because the cages are implanted in spongy bone, they are more likely to collapse the surrounding bone, thus resulting in loss of distraction and subsequently cage dislodgment.
U.S. Pat. No. 5,591,235 reports a certain spinal fixation device and technique for stabilizing vertebrae. In this technique, a hollow screw is inserted into a hole, preferably a hole saw recess, in each adjoining vertebrae. A channel is out into the vertebrae, which is lined up with corresponding axial slots in the screw. A rod is inserted into the channel and so as to pass through the axial slots in the screw. The rod is secured to each of the screws by means of a locking cap. The rod also is arranged so as to provide a bridge between the hollow screws in the adjoining vertebrae. Certain disadvantages have been surmised using such a device and technique. For example, it has become apparent that the trough in the vertebral bodies destabilizes some of the cortex of the vertebrae body wall, which is the strongest component.
In addition to fixation or fusion of vertebral columns, the prior art also describes methods or other spinal repair procedures, such as discectomy wherein an artificial disc or prosthetic device is placed within the vertebrae of the spine. For such prior art methods and related devices, there have been short comings such as having difficulty in securing the prostheses within the vertebral space or resulting in significant modification or damage to the load bearing surfaces of the vertebrae in an effort to secure the prosthesis.
Another method or other spinal repair technique involves augmentation of the nucleus of an intervertebral disk of the spine. The intervertebral disk is a flexible cartilaginous structure that is disposed between adjacent vertebrae. These disks form joints between the bodies of the vertebrae, which serve to unite adjacent vertebrae and to permit movement between them. These disks also play a role as shock absorbers when force is transmitted along the vertebral column during standing and movement.
Each disk is formed of two parts, a central mass called the nucleus pulpsous (herein the nucleus) and a surrounding fibrous layer, the annulus fibrosus (herein the annulus). The nucleus has a semi-gelatinous consistency, which allows it to become deformed when pressure is placed upon it, enabling the disk to change shape as the vertebral column moves.
There is described in U.S. Pat. Nos. 5,047,055; 5,824,093 6,264,695; the teachings of which are incorporated herein by references, various techniques and/or prosthetics for use in replacing or augmenting a spinal disc nucleus. Given the structure of the disk and its location between adjacent vertebrae, it is not a simple task to access the nucleus for the insertion of such prosthetics or materials to augment the nucleus. One technique for accessing the nucleus contemplates using the defect in the annulus, however, in practice the defect usually needs to be enlarged to allow the insertion of the prosthetic. Another technique contemplates having the surgeon drill through one of the adjacent bodies using a lateral approach. This another technique relies heavily on the skill and dexterity of the surgeon not to damage surrounding tissues, nerves and blood vessels. Also, the holed formed by such drilling is not easily sealed because of its shape and configuration.
Conventional techniques relating to fixation of the spine and bony structure rely in great part on the skill and dexterity of the surgeon to control the devices and instrumentalities being used to protect surrounding tissues, muscles, nerves and blood vessels from damage during the procedure. This is so because the devices and/or instrumentalities that the surgeon uses during such techniques, themselves do not provided the surgeon with a mechanism to protect the tissues, muscles, nerves and blood vessels surrounding the treatment or target area within the body from coming into contact with the device or instrumentality during the procedure. Consequently, the surgeon must use surgical techniques to relocate tissues, muscles, nerves and blood vessels from the surgical field, if that is possible, and for those which it is not possible, the surgeon must take care in the use of the device or instrumentality to prevent injury. It should be recognized that the surgeon while inserting and retracting or removing the device or instrumentality from the bony structure or spine must exercise such care to prevent injury.
Thus, it would be desirable to provide a new apparatus, system and methods for bony fixation that enhances healing of the bone while providing structural support therefore. It would be particularly desirable to provide such an apparatus, system and method that would involve the use of open surgical or minimally invasive surgical techniques as well as a technique in which the implant burrows in the structure of the bone; more particularly a technique in which the implant burrows in the bone spine, traverses across the disk space, and ends in an adjacent or neighboring vertebrae or vertebras, providing limited or no protrusions. It also would be desirable to provide such an apparatus, system and method where the implant is retained within the bone without requiring external fixation including contour-varying external vertebral wall fixation as compared to conventional devices, as such a device would avoid many of the problems associated with conventional devices such as blood vessel injury, erosion into organs, as well as placement near nerves. It also would be desirable for such apparatuses and systems to be adaptable for use in a wide range of procedures and techniques, including but not limited to augmentation of the nucleus such as by use of prosthetics.